a. Field of the Invention
The invention relates to a backlight module.
b. Description of the Related Art
FIG. 5 shows a schematic diagram illustrating a conventional display device having two different viewing angles. Referring to FIG. 5, a display device 100 includes a light guide plate 102, a right-side light source 104, a left-side light source 106, a parallax film 108 and a display panel 110. The right-side light source 104 and the left-side light source 106 are alternately turned on and off in succession, and the parallax film 108 deflects light beams emitted by the right-side light source 104 towards the left-hand side and light beams emitted by the left-side light source 106 towards the right-hand side, respectively. Accordingly, two eyes of a viewer receive light beams having two different light-emitting angles respectively to achieve a stereoscopic (three-dimensional) visual effect. However, for example, when the left-side light source 106 is turned on, a part of the light beams emitted by the left-side light source 106 (such as a light beam IL) is incident on a right-side surface 102a of the light guide plate 102 and reflected by the right-side surface 102a, as shown in FIG. 6. In that case, the light beam IL is guided towards an incorrect or unexpected direction. This may result in optical crosstalk and adversely affect image quality and brightness.
U.S. Pat. No. 7,528,893 discloses a backlight module for a stereoscopic display device, wherein a light guide plate of the backlight module includes a light-emitting surface, a first light incident surface, and a second light incident surface opposite the first light incident surface. A lot of anti-refection features are disposed on the first light incident surface and the second light incident surface. Each of the anti-refection features has at least two surfaces, and each of the surfaces is spread with a light absorption layer. Though this design may reduce optical crosstalk, the anti-refection features are difficult to be fabricated and need to be specifically defined an entrance to pass the light. This may result in complicated fabrication processes and considerable fabrication costs. U.S. Pat. No. 7,576,805 discloses a stereoscopic display device having a light guide plate and two light sources. A light transmission portion and an anti-reflection portion are formed on two ends of the light guide plate, and the anti-reflection portion serves the purpose of reducing optical crosstalk. However, in this design, inclined surfaces need to be formed on a specific position. Such design would result in complicated fabrication processes. Further, Taiwan patent application publication No. 200821708 discloses a backlight module having a light guide plate. The light guide plate includes a plate, at least one first notch, and at least one second notch. The first notch is formed on a side of the plate, the second notch is formed at the bottom of the first notch and the side of the plate, and the bottom of the second notch is substantially in the shape of a trapezoid.